Correct cup component placement during hip replacement or hip resurfacing procedures plays an important role for long-term success of the surgery. Non-optimal cup positioning can result in limited post-operative hip range of motion and can significantly increase the risk of dislocation of the femoral component.
Various image-guided and image-free computer-assisted systems have been proposed. All such systems are based on the installation of a tracking device in the operating room and attachment of sensors to the acetabulum and instruments. Furthermore, a computer-system is installed in the operating room, which displays the position of the instrument with respect to the planned cup position.
During such conventional procedures the surgeon orients the instruments to prepare the acetabulum and to impact the cup component into its final position by aligning them with accessible anatomical landmarks. During this procedure, the surgeon has visual access to only a very limited part of the anatomy, which does not represent the global alignment of the pelvis. This can result in misalignment of the cup component. Proposed computer-assisted solutions reduce this problem by planning the positioning of the cup component using pre- or intra-operative 3-D image modalities of the full pelvis. To transfer this planning into the patient's anatomy, registration between anatomy and planning is performed using locally accessible anatomical structures. On the other hand, to track the relative motion between anatomy and instruments, invasive fixation of the sensor to the anatomy and instruments, and the installation of expensive tracking technology in the operating theatre are necessary. The attached sensors are often prone to line-of-sight problems, which increase the complexity of the procedure. Furthermore, the registration procedure is often time consuming.